Recent activity

The geomagnetic field was quiet to minor storm on September 2. Solar wind speed ranged between
503 and 619 km/s (average speed was 568 km/s, increasing 115 km/s over the previous day)
under the influence of a high speed stream from CH288.

Solar flux measured at 20h UTC on 2.8 GHz was 69.4. The planetary A index
was 23 (STAR Ap - based on the mean of three hour interval ap
indices: 23.4). Three hour interval K indices: 45344243 (planetary),
35353342 (Boulder).

The background x-ray flux is below the class A1 level.

At midnight there was 1 spotted region on the visible solar disk. The solar flare activity
level was very low. No C class events were recorded during the day.

Region 10970 decayed slowly and was mostly quiet.

Coronal mass ejections (CMEs)

August 31 - September 2: No obvious fully or partly Earth directed CMEs were observed
in incomplete LASCO imagery.

Coronal holes

A recurrent coronal hole (CH288) in the southern hemisphere was in an
Earth facing position on August 28-29. A recurrent coronal hole (CH289) in the
southern hemisphere was in an Earth facing position on September 2.

Processed SOHO/EIT 195 image at 23:36 UTC on September 2. The
darkest areas on the solar disk are likely coronal holes.

Propagation

Long distance low and medium
frequency (below 2 MHz) propagation
along east-west paths over high and upper middle latitudes is poor to very poor. Propagation on long distance northeast-southwest paths
is fair to poor.

Monitoring remarks from a location near N58E06: August 31 - September
1: Relatively strong signals were noted from many TA stations from Newfoundland
in the north to Argentina in the south. 1350 Radio Buenos Aires was excellent at
23:15 UTC while at the same time 1400 CBG was strong. Later on lots of signals
from the USA (east coast), the Caribbean and northern South America were audible
at fair to good levels.

Forecast

The geomagnetic field is
expected to be quiet to unsettled
on September 3 due to effects from CH288.
Mostly quiet conditions are likely on September 4-5 while a high speed stream
from CH289 could cause a few unsettled and active intervals on September 6.

Coronal holes (1)

Coronal mass ejections (2)

M and X class flares (3)

1) Effects from a coronal hole could reach Earth
within the next 5 days. When the high speed stream has arrived the
color changes to green.
2) Effects from a CME are likely to be observed at Earth within 96
hours.
3) There is a possibility of either M or X class flares within the next
48 hours.

Data for all numbered solar regions according to the Solar Region
Summary provided by NOAA/SEC. Comments are my own, as is the
STAR spot count (spots observed at or inside a few hours before
midnight) and data for regions not numbered by SEC or where SEC has
observed no spots.
SEC active region numbers in the table below and in the active region
map above are the historic SEC/USAF numbers.

Active region

Date numbered

SEC
spot
count

STAR
spot
count

Location at midnight

Area

Classification

Comment

10970

2007.09.01

4

2

S07W21

0030

CSO

classification was DSO at midnight

Total spot count:

4

2

SSN:

14

12

Monthly solar cycle data

Month

Average solar
flux at Earth

International sunspot number

Smoothed sunspot number

2000.04

184.2

125.5

120.8
cycle 23 sunspot max.

2000.07

202.3

170.1

119.8

2001.12

235.1

132.2

114.6 (-0.9)

2006.07

75.7

12.2

15.3 (-1.0)

2006.08

79.0

12.9

15.6 (+0.3)

2006.09

77.8

14.4

15.6 (+0.0)

2006.10

74.3

10.4

14.2 (-1.4)

2006.11

86.3

21.5

12.7 (-1.5)

2006.12

84.5

13.6

12.1 (-0.6)

2007.01

83.3

16.9

12.0 (-0.1)

2007.02

77.7

10.6

11.6 (-0.4)

2007.03

72.2

4.8

(11.1 predicted, -0.5)

2007.04

72.4

3.7

(10.7 predicted, -0.4)

2007.05

74.4

11.7

(10.2 predicted, -0.5)

2007.06

73.7

12.0

(10.0 predicted, -0.2)

2007.07

71.6

10.0

(10.0 predicted, +0.0)

2007.08

69.1

6.2

(10.3 predicted, +0.3)

2007.09

70.1 (1)

1.4 (2)

(11.5 predicted, +1.2)

1) Running average based on the
daily 20:00 UTC observed solar flux
value at 2800 MHz.
2) Unofficial, accumulated value based on the Boulder (NOAA/SEC)
sunspot number. The official international sunspot number is typically
30-50% lower.

This report has been prepared by Jan
Alvestad. It is based partly on my own observations and analysis,
and
partly on data from some of these solar data sources.
All time references are to the UTC day. Comments and suggestions are
always welcome.